legacy turbo problem
 

hi i have a 91 legacy turbo, the problem is when i floor it there seems to b alot of lag and not much boost. sometimes it is better than others, also wen floor it from 1000rpm at about 4 -5 it goes mad and the revs go up and dwn and the car jerks about. it is ok if i rev up to about 5 rpm and then floor it although today it did it at 6 rpm which is weird, it has had a turbo upgrade and i was mady thinkin that hasnt been set up right or summit. if anyone know wat is up please help.